Modular pinion shaft for reciprocating pumps

ABSTRACT

A modular pinion shaft that includes a tubular member having a first end and a second end, a first pinion gear member secured to the first end by a plurality of fasteners, and a second pinion gear member secured to the first end by a plurality of fasteners. Gear teeth of each of the pinion gear members are aligned by one or more indexing members disposed between the tubular member and each pinion gear member.

BACKGROUND Field

Embodiments of the disclosure relate to a modular pinion shaft used in pressurized fluid delivery systems, such as reciprocating pumps commonly used in the oil and gas industry.

Description of the Related Art

Pressurized fluid delivery systems utilized in the oil and gas industry include fracturing pumps and mud pumps. These types of pumps are frequently driven by a single pinion shaft, or drive shaft, that is engaged at opposing ends with bull gears of a crankshaft. Alignment of the gear teeth between the pinion shaft and the bull gears is critical to prevent damage. Errors of even a few microns in the alignment influence gear capacity and life.

Pinion shafts are typically machined from a single piece of high quality tool steel that is subsequently heat treated. Teeth for engaging the bull gear teeth are machined on opposing ends of the single piece shaft. Timing of the teeth between the pinion shaft and the bull gears requires the manufacturer to hold tight tolerances.

While lengths of the pinion shafts vary, manufacture of the pinion shafts requires larger, more expensive machines, as well as larger heat treating furnaces. In addition, tolerances, particularly in the gear teeth on opposing ends of the pinion shaft, are difficult to hold as length increases. These problems make manufacturing difficult and expensive, and errors in gear timing may shorten the lifetime of the pinion shaft and/or the bull gears. Additionally, when the gear teeth fail, the entire pinion shaft must be replaced.

Therefore, there exists a need for new and improved pinion shafts.

SUMMARY

In one embodiment, a modular pinion shaft includes a tubular member having a first end and a second end. A first pinion gear member is secured to the first end by a plurality of fasteners. A second pinion gear member is secured to the first end by a plurality of fasteners. Gear teeth of each of the pinion gear members are aligned by one or more indexing members disposed between the tubular member and each pinion gear member.

In one embodiment, a method for manufacturing a pinion shaft includes securing a first pinion gear member to a first end of a tubular by a plurality of fasteners, securing a second pinion gear member to a second end of the tubular member by a plurality of fasteners, and providing one or more indexing members disposed between the tubular member and each pinion gear member.

BRIEF DESCRIPTION OF THE DRAWINGS

Having generally described the various embodiments of the disclosure, reference will now be made to the accompanying drawings.

FIGS. 1 and 2 are isometric views of a modular pinion shaft according to one embodiment.

FIG. 3A is a sectional view of the modular pinion shaft along lines 3A-3A of FIG. 2.

FIG. 3B is an enlarged view of a portion of the modular pinion shaft of FIG. 3A.

FIGS. 4 and 5 are end views of the modular pinion shaft.

FIG. 6 is a schematic sectional view of a reciprocating pump where the embodiments of the modular pinion shaft may be utilized.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.

DETAILED DESCRIPTION

Embodiments described herein relate to a pinion shaft having a robust modular (e.g. multi-piece) design that is easier and cheaper to manufacture, provides enhanced serviceability, and minimizes operational issues as compared to conventional single piece pinion shafts. As the need for larger and long pinion shafts increases, the drawbacks and costs of conventional single piece pinion shafts also increase due to the need for larger, more expensive equipment to handle, machine, and heat treat such large pinion shafts. Further, holding tight tolerances of gears at one end of the pinion shaft to gears at the other end becomes more difficult over long distances, which may disrupt critical gear timing.

FIGS. 1 and 2 are isometric views of a modular pinion shaft 100 according to one embodiment. The modular pinion shaft 100 includes a tubular member 105 having a first end 108A and a second end 108B. Each of the first end 108A and the second end 108B include a coupling interface for attaching pinion gear members 110 to the tubular member 105.

In the embodiment shown, each of the pinion gear members 110 may include a bearing surface 115 positioned inwardly of gear teeth 120. However, in other embodiments, the gear teeth 120 may be located inward of the bearing surface 115. One of the pinion gear members 110 may include an extended shaft portion 125 for coupling with a power source, such as a motor. The extended shaft portion 125 may include a keyway 130, such as a groove, formed along a longitudinal length of the extended shaft portion 125. In one embodiment, the extended shaft portion 125 may include splines formed along a longitudinal length of the extended shaft portion 125 instead of or in addition to the keyway 130.

Fasteners 135, such as bolts, may be used to secure the pinion gear members 110 to the tubular member 105. In contrast to conventional pinion shafts, which are machined from a single piece of material, the pinion gear members 110 are removable and replaceable. Thus, a damaged pinion gear can be replaced with a new pinion gear member 110. This saves costs as the entire modular pinion shaft 100 would not need to be replaced.

FIG. 3A is a sectional view of the modular pinion shaft 100 along lines 3A-3A of FIG. 2. The tubular member 105 includes a hollow center 300 which decreases the weight of the modular pinion shaft 100. Coupling interfaces 305 between the tubular member 105 and the pinion gear members 110 are shown in FIG. 3A. Each coupling interface 305 may include a first bore 310 formed in a wall 315 of the tubular member 105. The first bore 310 may be utilized to receive an indexing member 320, which may be a pin.

The indexing member 320 may partially extend from faces 325 of the tubular member 105 at each of the first end 108A and the second end 108B. The extending portion of the indexing member 320 may be received in a second bore 330, such as a mating bore, formed in the pinion gear members 110. The indexing member 320 may be used to ensure that the gear teeth 120 of the pinion gear members 110 are aligned properly relative to each other and/or relative to any gears that will mate up with the pinion gear members 110 for correct gear timing.

FIG. 3B is an enlarged view of a portion of the modular pinion shaft 100 of FIG. 3A. Each coupling interface 305 may include a recessed portion that receives a portion of the pinion gear member 110. The recessed portion is formed by a shoulder 340 of the wall 315 at the first end 108A and the second end 108B of the tubular member 105. The shoulder 340 may be formed in the face 325 of the tubular member 105 at the inside diameter of the tubular member 105. The pinion gear member 110 may include a face 345 that extends into the recessed portion and contacts the shoulder 340.

FIGS. 4 and 5 are end views of the modular pinion shaft 100. FIG. 4 shows the first end 108A of the modular pinion shaft 100, and FIG. 5 shows the second end 108B of the modular pinion shaft 100. The modular pinion shaft 100 may include one or more indexing members 320 on each of the first end 108A and the second end 108B. As shown in FIGS. 4 and 5, the indexing members 320 may be at least partially disposed in through-holes 500 (as opposed to a second bore 330 shown in FIG. 3A) formed in the pinion gear members 110 such that an end of each indexing member 320 is visible.

FIG. 6 is a schematic sectional view of a reciprocating pump 600 where the embodiments of the modular pinion shaft 100 may be used. The reciprocating pump 600 is of a type typically utilized for oil and gas well service operations, such as pumping high pressure fluid into a well to hydraulically fracture the reservoir. The reciprocating pump 600 may also be configured for pumping drilling fluid into the well during drilling.

The reciprocating pump 600 may include a power source 605, such as a motor, operably coupled to the modular pinion shaft 100 to rotate the modular piston shaft 100. The modular pinion shaft 100 includes the pinion gear members 110 on both ends of the tubular member 105 (only one pinion gear member 110 is shown). The gear teeth on the pinion gear members 110 mate with gear teeth on corresponding bull gears 610 (only one bull gear 610 is shown) to drive the bull gears 610, which are connected to a crankshaft 615. The modular pinion shaft 100 is supported in a housing 616 of the reciprocating pump 600 by bearings 618 (only one is shown).

One or more connecting rods 620 are coupled to the crankshaft 615. Each connecting rod 620 is connected to a crosshead 625, and each crosshead 625 moves in a linear stroke within a stationary crosshead casing 630. A pony rod 635 secures each crosshead 625 to a plunger 640 disposed in a fluid end 645. Tie rods 650 connect the fluid end 645 to an end portion of the reciprocating pump 600. As the plunger 640 is stroked, fluid is brought into the fluid end 645 from an intake 655 and discharged at higher pressure out a discharge 660.

Timing of the gear teeth between the pinion gear members 110 of the modular pinion shaft 100 and the bull gears 610 is critical to the operation and performance of the reciprocating pump 600 and thus the fluid end 645. A principal factor of a properly timed reciprocating pump is ensuring that the gear teeth of the pinion shaft on one end exactly match the gear teeth of the pinion shaft on the other end in both size and orientation so that they mate correctly at each end with corresponding bull gears. The modular pinion shaft 100 as described herein minimizes tolerance errors as well as timing of the gear teeth by utilizing the indexing members 320 to ensure that the gear teeth on each of the pinion gear members 110 are properly aligned when coupled to the tubular member 105.

Also, reciprocating pumps operate in a harsh environment which may cause the gear teeth to fail due to bending, wear, or shear. When this happens to a conventional single piece pinion shaft, the entire pinion shaft must be replaced. However, the modular pinion shaft 100 as described herein allows the end user to replace one or both pinion gear members as needed, which reduces the cost of repairs by up to 80 percent.

Further, heat treating of a single piece pinion shaft after it has been machined may cause problems. Longer single piece pinion shafts tend to move (e.g. expand, bend, twist) during a heat treatment process, which makes it difficult to holding tight tolerances between the gears at opposite ends of the pinion shafts. The tubular member 105 and the pinion gear members 110 of the modular pinion shaft 100 however may be heat-treated separately, which increases the ability to control tolerances of the gears on the pinion gear members 110 and reduces the size of the furnace needed for heat treatment compared to heat treating a very long single piece pinion shaft. The tubular member 105 of the modular pinion shaft 100 may be machined after heat treating so that the material properties can be optimized.

Another issue inherent with a single piece pinion shaft is that the material is exactly the same for the gear teeth and the middle portion of the single piece pinion shaft. However, the material of the tubular member 105 and the pinion gear members 110 may be different and may be chosen as needed for optimal performance of the modular pinion shaft 100. For example, one pinion gear member 110 at one end of the modular pinion shaft 100 can be made out of a material that is different than the material which the pinion gear member 110 located at the opposite end is made out of. For another example, one or both of the pinion gear members 110 can be made out of one material that can handle higher stresses, whereas the tubular member 105 can be made out of a different material that is lighter in weight to reduce the overall weight of the modular pinion shaft 100. Considerations may include cost and/or availability of different materials that may be utilized for the fabrication of the modular pinion shaft 100.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

We claim:
 1. A modular pinion shaft, comprising: a tubular member having a first end and a second end; a first pinion gear member secured to the first end by a plurality of fasteners; and a second pinion gear member secured to the second end by a plurality of fasteners, wherein gear teeth of each of the pinion gear members are aligned by one or more indexing members disposed between the tubular member and each pinion gear member.
 2. The modular pinion shaft of claim 1, wherein each of the first and second ends include a recessed portion that receives a portion of a respective pinion gear member.
 3. The modular pinion shaft of claim 1, wherein an end of the each of the one or more indexing members is disposed in a bore formed in the pinion gear members.
 4. The modular pinion shaft of claim 3, wherein the bore is a through-hole formed in the pinion gear members.
 5. The modular pinion shaft of claim 1, wherein each of the pinion gear members include a bearing surface.
 6. The modular pinion shaft of claim 5, wherein the bearing surface is positioned inward of the gear teeth.
 7. The modular pinion shaft of claim 1, wherein the pinion gear members comprise a first material and the tubular member comprises a second material different than the first material.
 8. A method for manufacturing a pinion shaft, the method comprising: securing a first pinion gear member to a first end of a tubular by a plurality of fasteners; securing a second pinion gear member to a second end of the tubular member by a plurality of fasteners; and providing one or more indexing members disposed between the tubular member and each pinion gear member.
 9. The method of claim 8, further comprising heat treating the pinion shaft, wherein the tubular member and the pinion gear members are heat treated separately.
 10. The method of claim 9, wherein the tubular member comprises a first material and the pinion gear members comprise a second material.
 11. The method of claim 10, wherein the first material is different than the second material.
 12. The method of claim 8, wherein the pinion gear members comprise a first material and the tubular member comprises a second material different than the first material.
 13. The method of claim 12, further comprising heat treating the pinion shaft, wherein the tubular member and the pinion gear members are heat treated separately. 